Embodiments of the present invention relate to configurable multi-mode peripheral devices. More specifically, embodiments of the present invention relate to peripheral devices that can be dynamically configured and reconfigured independently of a host device.
A peripheral device may be coupled to a host device using a variety of different cables, connectors and buses. One mechanism for coupling devices that is growing in favor and use is a Universal Serial Bus (USB). A USB provides a standardized and high bandwidth connection between a peripheral device and a host device. A USB typically supports operation in different modes. For example, the peripheral device and the host device may communicate at different rates depending on a selected mode of operation. The standard modes of operation include a low-speed mode, a full-speed mode, and a high-speed mode.
However, changing the operating mode of a conventional USB device (that is, a USB-compatible peripheral device) can be problematic. In one conventional approach, operation at low speed and at full speed is supported. However, the USB device is hard-wired into one mode or the other. To change modes, USB configuration resistors and phase-locked loop (PLL) settings need to be changed. Changing the PLL settings requires powering off the peripheral device, changing a jumper, and then restarting the device.
In another conventional approach, a peripheral device and USB are initialized according to configuration information downloaded from a host device. To change operating mode, new configuration information is downloaded from the host device. The peripheral device is disconnected from the host device, reconfigured according to the new configuration information, and reconnected to the host device. While this latter approach provides some advantages over the first approach, in some circumstances the change in mode may be problematic because intervention by the host device is needed. The dependency of the peripheral device on the host device can limit the flexibility of the peripheral device.
Another conventional approach allows the peripheral device and the host device to in essence agree on a mode of operation, with the peripheral device then implementing a configuration accordingly. For example, the peripheral device may initially attempt to establish a high-speed connection with the host device. If such a connection is not available from the host device, the peripheral device falls back to a full-speed mode. However, this approach is problematic because subsequent attempts to reconfigure the peripheral device for a different mode of operation are encumbered by the problems described above.
Therefore, what is needed is a peripheral device that can be configured and reconfigured without encountering the aforementioned problems. What is also needed is a device that can satisfy this need for USB. The present invention provides a novel solution to these needs.
Embodiments of the present invention pertain to a device that can be configured and reconfigured for different operating modes independent of a host device.
In one embodiment, the device includes a controller for selecting a mode of operation. The device is configured according to the mode of operation. The configuration information corresponding to the mode of operation resides on the device such that the configuring is accomplished independent of a host device. In this embodiment, the device also includes interface circuitry for simulating disconnection of the device from, and reconnection of the device to, the host device. The selected mode of operation is implemented between the simulated disconnection and reconnection.
In one embodiment, the interface circuitry is couplable to a Universal Serial Bus (USB) that couples the device to the host device. The USB remains coupled to the device and the host device while the disconnection and reconnection are simulated. In this embodiment, a first data line and a second data line are coupled to the interface circuitry. A supply voltage is selectively coupled to one of the data lines according to which mode of operation is selected. By monitoring the data lines the host device can determine the mode of operation of the peripheral device.
In another embodiment, the selected mode of operation characterizes a rate at which data are communicated with the host device via the interface circuitry. In one such embodiment, the device also includes a data processor. The data processor processes data according to the rate at which data are communicated with the host device.
In yet another embodiment, the device includes a clock generator that operates at a speed corresponding to the selected mode of operation.